Reduction of Collection Efficiency of Charge Carriers with Increasing Cell Size in Polymer Bulk Heterojunction Solar Cells

Changes in solar cell performance related to active area size were investigated using polymer bulk heterojunction devices. Cell geometry was defined by introduction of a sub-electrode. The cells were uniform up to 16 cm2. The solar cells showed little change in performance up to a cell area of 1 cm2. As cell area increased above 4 cm2 the power conversion efficiency dropped significantly, mostly because of fill factor (FF) drop and short circuit current density (Jsc) suppression. The changes in FF and Jsc could not be described solely by a Shockley diode equation based on an equivalent circuit model unless photocurrent collection was also considered. As cell area increased, collection efficiency deviated from unity, which further reduced device performance. That deviation is attributed to acceleration of recombination loss at low built-in junction potentials.

[1]  Barry P Rand,et al.  4.2% efficient organic photovoltaic cells with low series resistances , 2004 .

[2]  Lei Zhang,et al.  Energy losing rate and open-circuit voltage analysis of organic solar cells based on detailed photocurrent simulation , 2009 .

[3]  Carl M. Lampert,et al.  Editorial: Reporting solar cell efficiencies in Solar Energy Materials and Solar Cells , 2008 .

[4]  N. E. Coates,et al.  Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing , 2007, Science.

[5]  Jan Genoe,et al.  Analytical model for the open-circuit voltage and its associated resistance in organic planar heterojunction solar cells , 2008 .

[6]  S. Forrest,et al.  Controlled growth of a molecular bulk heterojunction photovoltaic cell , 2004 .

[7]  B. Ghosh,et al.  Series resistance and optimum grid design for a thin film solar cell of rectangular shape , 1984 .

[8]  Nelson E. Coates,et al.  Bulk heterojunction solar cells with internal quantum efficiency approaching 100 , 2009 .

[9]  L. Jay Guo,et al.  Choice of electrode geometry for accurate measurement of organic photovoltaic cell performance , 2008 .

[10]  R. J. Handy.  Theoretical analysis of the series resistance of a solar cell , 1967 .

[11]  Germà Garcia-Belmonte,et al.  Determination of gap defect states in organic bulk heterojunction solar cells from capacitance measurements , 2009 .

[12]  N. C. Wyeth,et al.  Sheet resistance component of series resistance in a solar cell as a function of grid geometry , 1977 .

[13]  A. Rothwarf,et al.  Effects of a voltage‐dependent light‐generated current on solar cell measurements: CuInSe2/Cd(Zn)S , 1984 .

[14]  Valentin D. Mihailetchi,et al.  Charge Transport and Photocurrent Generation in Poly(3‐hexylthiophene): Methanofullerene Bulk‐Heterojunction Solar Cells , 2006 .

[15]  V. Mihailetchi,et al.  Photocurrent generation in polymer-fullerene bulk heterojunctions. , 2004, Physical review letters.

[16]  Jenny Nelson,et al.  Diffusion-limited recombination in polymer-fullerene blends and its influence on photocurrent collection , 2003 .

[17]  Mario Leclerc,et al.  A Low‐Bandgap Poly(2,7‐Carbazole) Derivative for Use in High‐Performance Solar Cells , 2007 .

[18]  C. Brabec,et al.  Origin of the Open Circuit Voltage of Plastic Solar Cells , 2001 .

[19]  Gang Li,et al.  Accurate Measurement and Characterization of Organic Solar Cells , 2006 .

[20]  Mark A. Ratner,et al.  Efficiency Enhancement in Organic Photovoltaic Cells: Consequences of Optimizing Series Resistance , 2010 .

[21]  S. Hegedus.  Current–Voltage Analysis of a-Si and a-SiGe Solar Cells Including Voltage-dependent Photocurrent Collection , 1997 .

[22]  Gang Li,et al.  Highly efficient inverted polymer solar cell by low temperature annealing of Cs2CO3 interlayer , 2008 .

[23]  Gang Li,et al.  For the Bright Future—Bulk Heterojunction Polymer Solar Cells with Power Conversion Efficiency of 7.4% , 2010, Advanced materials.

[24]  Michael D. McGehee,et al.  Photovoltaic cells made from conjugated polymers infiltrated into mesoporous titania , 2003 .

[25]  Effect of electrode geometry on the photovoltaic performance of dye-sensitized solar cells , 2009 .

[26]  Yang Yang,et al.  Polymer solar cells with enhanced open-circuit voltage and efficiency , 2009 .

[27]  Hong Ma,et al.  High performance ambient processed inverted polymer solar cells through interfacial modification with a fullerene self-assembled monolayer , 2008 .

[28]  S. Hegedus,et al.  Voltage dependent photocurrent collection in CdTe/CdS solar cells , 2007 .

[29]  Yang Yang,et al.  High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends , 2005 .

[30]  A J Heeger,et al.  Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols. , 2007, Nature materials.

[31]  Ye Tao,et al.  Highly efficient polycarbazole-based organic photovoltaic devices , 2009 .

[32]  Paul R. Berger,et al.  4.8% efficient poly(3-hexylthiophene)-fullerene derivative (1:0.8) bulk heterojunction photovoltaic devices with plasma treated AgOx/indium tin oxide anode modification , 2008 .

[33]  C. Deibel,et al.  Photocurrent in bulk heterojunction solar cells , 2010, 1001.2546.

[34]  Ye Tao,et al.  Toward a rational design of poly(2,7-carbazole) derivatives for solar cells. , 2008, Journal of the American Chemical Society.

[35]  Neil C. Greenham,et al.  Modeling the current-voltage characteristics of bilayer polymer photovoltaic devices , 2003 .

[36]  K. S. Narayan,et al.  Area dependent efficiency of organic solar cells , 2008 .

[37]  Christoph J. Brabec,et al.  Characterization of Organic Solar Cells: the Importance of Device Layout , 2007 .

[38]  V. Mihailetchi,et al.  Cathode dependence of the open-circuit voltage of polymer:fullerene bulk heterojunction solar cells , 2003 .

[39]  Christoph J. Brabec,et al.  High Photovoltaic Performance of a Low‐Bandgap Polymer , 2006 .

[40]  André Moliton,et al.  Size effect on organic optoelectronics devices: Example of photovoltaic cell efficiency , 2008 .

[41]  Bernard Kippelen,et al.  Area-scaling of organic solar cells , 2009 .

[42]  Yi-Kai Lin,et al.  Modified buffer layers for polymer photovoltaic devices , 2007 .